Apologies if this has been posted previously.
As most spam seems to come from dodgy sites that sell your e-mail address on whenever you register with them, it is useful to be able to use a disposable e-mail address that expires after a pre-determined number of messages have been sent. I use disposable addresses from Spamgourmet whenever I am registering with a Software company, games site etc. Used in conjunction with a permanent spam bucket such as a webmail account, I find that I receive hardly any spam at all in my pop3 mail.
http://www.spamgourmet.com